Apparatus for supporting the tire of a vehicle so that the latter can be moved without touching the ground are well known. Typically, the apparatus comprises a plurality of wheels attached to a frame adapted to support the vehicle tire and a means for mounting the vehicle tire onto the means for support.
A variety of alternative frames, supports, and mounting members are known. In English patent application no. 2,109,313, Murillo discloses a three-wheeled trolley for use with vehicles having a flat or damaged tire. The vehicle tire is driven onto the trolley via a drive-on part which is rotated into position and then is clamped fast, the tire being supported at the rear side by the drive on part and resting at the front end against another supporting part which is also rotatable, while the bottom of the tire rests on the floor of a tray which hangs under the frame. In order to insure that the trolley remains in place when driving a tire onto it, the drive-on part is equipped on its underside with a protruding part which, in the non-rotated condition, lifts up the trolley, so that the rear wheels are free from the surface below.
This known trolley has a number of disadvantages, as for example the need for a separate clamp to prevent dislodging of the tire when the trolley is driving along bumpy road or otherwise subjected to pressures which tend to dislodge it. Further, the trolley has relatively large dimensions, which makes it difficult to carry or fit in a vehicle's storage area.
In. U.S. Pat. No. 4,726,727, Tyler discloses a six-wheeled trolley with a drive-on ramp, two braking systems to prevent movement of the trolley while mounting or dismounting a disabled vehicle tire, and a means to connect the trolley to the vehicle for safety and support while the vehicle and trolley are moving.
Tyler's trolley has a number of disadvantages, including the inherent instability of the disabled tire resting on a surface that is relatively flat, thereby not allowing the wheel to be sufficiently well-seated to withstand the forces that tend to dislodge it while the vehicle is in motion, thus necessitating attachment of the trolley to the vehicle. Further disadvantages include bulkiness, and closely spaced running wheels that increase the chances of the trolley being dislodged by irregularities in the surface upon which it is being driven. Moreover, the placement and large numbers of its wheels make turning of the vehicle more difficult and contribute to the instability of the vehicle tire on the trolley. Further, the Tyler trolley cannot be folded up for ease of handling and storage.
In U.S. Pat. No. 2,358,864, Lockwood discloses a wheel trolley comprising three wheels mounted on a frame, a drive-on part, and several fixed support members. Lockwood's apparatus suffers from several disadvantages, including the lack of a hinged frame, which causes the trolley to take up significant space when it is stored, and the requirement that the tire be supported in at least five points in order to achieve stability while in use.
In U.S. Pat. No. 3,720,422, Nelson discloses a trolley with an adjustable frame, but without a drive-on part. A disabled tire is mounted on the trolley by first jacking up the vehicle, then placing the trolley in position and lowering the tire onto it. The disadvantages of this apparatus are obvious as the driver of the vehicle is forced to spend time and considerable energy jacking up the car in order to use the trolley. Further, in this device lateral support for the vehicle tire is minimal, leaving the trolley vulnerable to accident in the event that it hits a large hole or object, or is subjected to forces that tend to dislodge the tire, such as sharp turns or fast stops.
In U.S. Pat. No. 3,583,723, Nowell teaches a trolley similar to that described by Nelson in that no drive-on part is provided. Further, as with Nelson, the three-sided trolley frame disclosed is inherently weaker than a four-sided frame as taught by the present invention.
In U.S. Patent Nos. 4,350,470 and 4,465,421, Murillo teaches a three-wheeled trolley with a drive-on part and support shelf hanging below the frame. Murillo does not teach a foldable frame nor does he teach self-adjusting and locking support members.
U.S. Ser. No. 044,810, with the same inventor and commonly assigned with the present invention, also discloses a wheel trolley with a foldable frame. Although this wheel trolley is said to perform satisfactorily, a couple of problems still exist, including the need to manually lock the support members into position once the tire has been driven onto the trolley or to rely upon the vehicle weight alone to hold the members in position, and the possibility, particularly if the disabled tire is a powered tire, of the tire running up the front support member at certain accelerations.